Yes, wow, I've heard the same thing. The caffeine is apparently spent in the first brewing of the leaves ~ if you want confirmation from an acknowledged expert, I'd suggest you contact the guy at
http://www.teasource.com. I don't remember his name, but he owns a tea specialty store in St Paul that I've been to several times, and he's been interviewed about tea on NPR. Ol' what's-his-name really knows his stuff.
(I looked around on the store website a little bit, but didn't find information useful to answering this question...)
Of course, in googling, I found
http://www.teatreasures.com/Teainfo.html, which confirms this idea:
"About 80 percent of the tea's caffeine content is released within the first 30 seconds of steeping. You
can enjoy all teas by decaffeinating the tea yourself by discarding the water after the first 30 seconds'
steeping, then adding fresh boiling water to the remaining leaves. Some say tea has constituents
which act to soothe and relax the body. These polyphenols begin to dissolve only in the third minute
of steeping. This is the secret to bedtime tea.
If you are cold, tea will warm you; if you are heated, it will
cool you; if you're depressed, it will cheer you; if you're excited, it will calm you.—Norwood Pratt
There is more caffeine in a pound of tea than in a pound of coffee. However, a pound of coffee
produces about 40 cups, whereas a pound of tea produces about 200 cups. Green tea has about
one-third as much caffeine as black tea, and oolong has about two-thirds as much."
